1. Field of the Invention
This invention relates to a vibration type density meter including a mechanical oscillator having a resonance frequency variable with the density of a fluid around the oscillator, and more particularly to such meter usable for small amounts of fluid, and also usable on desktops, such as in a laboratory.
2. Description of the Prior Art
Various densitometers for measuring fluid densities have been proposed priorly. For example, Japanese Patent Publication No. 43-26012 discloses a density meter having a tuning fork type tubular oscillator for introducing therein a fluid to be measured for its density. The oscillator is actuated to produce transverse free oscillations, the frequency of which is utilized to derive the density of the fluid. Another density meter is disclosed in Japanese Patent Publication No. 51-16794, and comprises a cylindrical resonator, within and outside of which a fluid to be measured flows along the wall of the resonator. The density of the fluid is derived from the frequency of looped oscillation of the cylindrical resonator excited.
These prior density meters leave much to be desired. For example, the former densitometer requires a sampling pump and associated parts for introducing the fluid to be measured, into the tubular oscillator. The latter density gage is required to have its cylindrical resonator installed in a pipe through which the fluid to be measured flows. The prior density indicators, therefore, have the disadvantages of awkward installation and operation. Furthermore, the known density meters are of such a design that they are unable to measure the density of a small amount of fluid, such as a sample in a test tube.